Bloodstain pattern analysis
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ASISTM Project Forensic Investigations. Bloodstain pattern analysis. What is bloodstain pattern analysis?. The bloodstain patterns left by falling, projected or smeared blood can be analysed by trained crime scene investigators.

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Bloodstain pattern analysis

ASISTM Project

Forensic Investigations

Bloodstain pattern analysis


What is bloodstain pattern analysis
What is bloodstain pattern analysis?

  • The bloodstain patterns left by falling, projected or smeared blood can be analysed by trained crime scene investigators.

  • Careful observation and measurement of the position and shape of bloodstains can give lots of information about the direction of travel, angle of impact and the speed or velocity of the blood droplets.


Definition
Definition

“Through the examination of bloodstains and bloodstain patterns, in association with knowledge of the underpinning sciences, they provide a determination of the physical events responsible for their deposition.”

RCMP - Royal Canadian Mounted Police


Why is it important in forensics
Why is it importantin forensics?

  • Bloodstain patterns can be used to prove or refute a suspect’s account of what happened.

  • The information from the bloodstain patterns can possibly be used to reconstruct a crime.

  • Bloodstain pattern analysis can tell us the “how” of a crime.


Blood
Blood

  • Blood is a fluid that makes up approximately 8% of the weight of a human body.

  • Females have approximately 4-5 litres while males have between 5-6 litres.

  • Blood is made up of cells (red blood cells and white blood cells) plus platelets in a yellowish liquid called plasma.

  • Plasma contains gases (oxygen, carbon dioxide) and molecules such as proteins, fats and carbohydrates (sugars).


Properties of blood
Properties of blood

  • Blood has certain properties that can be compared to water.


Surface tension
Surface tension

  • Surface tension is an upwards force that enables insects such as a water strider to “walk on water”.

Image:Water strider: David Cappaert, www.insectimages.org


Surface tension1
Surface tension

  • Surface tension enables blood droplets to maintain a sphere shape.

Image courtesy UWA PhD research student Mark Reynolds.


Traveling blood droplets
Traveling blood droplets

  • When a force is applied to a mass of blood, the blood breaks into droplets.

  • The droplets fly through the air as “perfect” spheres due to surface tension.

Image used with permission from Tom Bevel & Ross Gardner, June 2006.



Stage 1 contact collapse
Stage 1: contact & collapse

Image used with permission from Tom Bevel & Ross Gardner, June 2006.


Stage 2 displacement
Stage 2: displacement

Image used with permission from Tom Bevel & Ross Gardner, June 2006.


Stage 3 dispersion
Stage 3: dispersion

Image used with permission from Tom Bevel & Ross Gardner, June 2006.


Stage 4 retraction
Stage 4: retraction

Image used with permission from Tom Bevel & Ross Gardner, June 2006.


Height and size of blood drops
Height and size of blood drops

  • A blood droplet released from a 1m height will be smaller than a blood droplet released from a 1.5m height.

  • This is because the velocity of the blood droplet released from a higher height is greater.


Surface and shape of blood drops
Surface and shape of blood drops

Images courtesy DUIT Multimedia: Paul Ricketts.


Low impact
Low impact

  • Low impact is really blood under the influence of gravity - it just falls.

Image courtesy UWA PhD research student Mark Reynolds.


Medium impact
Medium impact

  • Medium impact occurs when a force such as a bat is applied.

Image courtesy UWA PhD research student Mark Reynolds.


High impact fine mist of droplets
High impact - fine mist of droplets

Image courtesy Stuart James, February 2007


Angle of impact
Angle of impact

Image used with permission from Stuart James, February 2007.


Origin of blood
Origin of blood

Image used with permission from Tom Bevel & Ross Gardner, June 2006.


Reconstructing the crime
Reconstructing the crime

  • With the evidence that is collected, the crime scene investigator attempts to reconstruct the crime.

  • This involves trying to work out what events happened and the order that they happened.

Image courtesy UWA PhD research student Mark Reynolds.


What other things you may need to know to reconstruct a crime
What other things you may need to know to reconstruct a crime

  • Forensic pathology results - post mortem information

  • Forensic biology results - eg, DNA

  • Witness statements

  • Impressions - fingerprints, shoeprints

  • Ballistics

  • Entomology evidence if appropriate


References
References crime

Bevel, T. & Gardner, R.M. 1997 Bloodstain Pattern Analysis. With an introduction to crime scene reconstruction. Boca Raton CRC Press LLC.

James S.H., Kish, P.E. & Sutton, T.P. 2005 Principles of bloodstain pattern analysis : theory and practice. Boca Raton, CRC Press LLC.

Mark Reynolds, PhD Research Student, Centre for Forensic Science The University of Western Australia.

Paul Ricketts, Photographer, DUIT Multimedia, The University of Western Australia.


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